There has been conventionally known the use of an LED substrate unit as energy-saving illumination which consumes less energy than other light sources.
Moreover, the LED substrate unit has been highly expected as a light source for a thin lighting apparatus excellent in design since it is smaller in size than other light sources for an incandescent lamp or a fluorescent lamp.
However, when the LED substrate unit emits light, considerably high heat is generated. If a temperature of an LED is increased due to the generated heat, conversion efficiency from electric energy into optical energy is degraded. As a result, it is impossible to make full use of the feature of a low energy consumption of the LED, and further, to prolong the lifetime of the LED.
In order to solve the above-described problems, a lighting apparatus disclosed in Patent Document 1 has been known in the related art. This conventional lighting apparatus is designed such that an LED-packaged substrate is incorporated directly in a pair of aluminum casings. This is for improving heat dissipation capacity by making full use of the characteristics of highly heat conductive aluminum. In addition, some contrivance has been taken for further improving the heat dissipation effect via a ventilation hole or a cutout by forming the ventilation hole or the cutout in the casing or LED-packaged substrate.
Patent Document 1: Japanese Patent Application Laid-Open No. 2006-179443
Patent Document 2: Japanese Patent No. 3965929